The present invention relates generally to removable covers for top loading industrial furnaces, such as soaking pits and, more particularly, to the beam structure which supports the rails upon which the covers are carried to and from their position over the openings in the several furnace chambers.
Furnaces of this type are normally arranged in batteries, each comprising a number of refractory-lined chambers within which ingots are heated to their rolling temperature of greater than 2000.degree. F. The openings through which access to the respective chambers is obtained are normally disposed on the top of the unit and are closed by large, heavy refractory-lined covers in order to retain the heat within the chambers. The covers are usually mounted on self-propelled, remote-controlled wheeled carriages which run on beam-supported rails whereby they can be conveniently manipulated to open or close the chamber openings when access to the interior is desired. For the sake of compactness, the rails associated with the covers of two adjacent chambers may be supported on the same support beam which is disposed along the top of the median wall that divides the two chambers. Support beams of the type referred to above are as shown and described in U.S. Pat. No. 2,920,769 which issued Jan. 12, 1960 to H. F. Spencer. Because of their proximity to the furnace chambers such support beams are subjected to severe thermal stressing due to constant heat conduction through the walls and framing structure of the furnace and to the intermittent exposure to the radient effects of the interior of the adjacent chambers when the covers are removed. Such thermal stressing, coupled with the heavy physical loading on the support beams renders them prone to excessive deflection. Oftentimes, when this occurs, only two of the four carriage wheels are caused to contact the rails thereby concentrating the reactive forces on the cover which, in severe cases, will cause cracking of the refractory lining and premature failure of the cover.
To remedy this condition and to extend the life of the beam structure, it has been proposed to increase the size of the support beam and to employ means for fluid cooling the same with water or air as the coolant. However, the use of a beam of increased size, besides adding significantly to the fabricating and operating cost of the furnace organization, also requires complete redesign and replacement of the cover carriage in order to accommodate a support beam of larger dimensions. Obviously, this need compounds the cost of the apparatus but, in addition, it imposes the additional requirement of having to incur the cost of maintaining the cooling system.
It is to the improvement of such apparatus, therefore, that the present invention is directed.